Problem: $\text B = \left[\begin{array}{rr}2 & 0 \\ -2 & 0\end{array}\right]$ What is the determinant of $\text B$ ?
Solution: The determinant of a 2x2 matrix can be computed the following way: $ \left|\begin{array}{rr}a & b \\ c & d\end{array}\right| = (a \times d)-(b \times c) $ In this specific case, $ \left|\begin{array}{rr}2 & 0 \\ -2 & 0\end{array}\right| = (2 \cdot 0)-(0 \cdot -2) $ $ = 0 $